The cerebral areas related to vision in the rhesus monkey were identified and delineated by applying the (14C) 2-deoxyglucose method and comparing metabolic activity (local rates of glucose utilization) in visually stimulated versus visually deafferented cerebral hemispheres. The visual-nonvisual borders of 1) an occipito-temporal visual pathway, and 2) an occipito-parietal visual pathway were determined and, further, their points of interaction with inferior prefrontal cortex, prearcuate, and with limbic, striatal, and diencephalic structures were specified. The functional contribution of the forebrain commissures to vision was quantified by comparing monkeys prepared with complete vs. partial visual deafferentation of one hemisphere (i.e. optic tract section plus forebrain commissurotomy vs. optic transection alone, respectively). Some of the cerebral areas serving multimodal functions were identified through a comparison of brain metabolism in monkeys given visual stimulation only and monkeys given visual plus somatosensory stimulation. Finally, the functional development of the visual system was traced in a series of infant monkeys. In these animals, metabolic activity appears to reach adult levels at about 4 months of age.